It's based on the real-world company Goodyear where tires is their specialty.
GTA San Andreas
TransFender and Wheel Arch Angels offer Atomic brand custom rims. Wheel Arch Angels also offers an Atomic-themed paint job for the Flash. However, this Atomic might not be related to the HD version of Atomic.
In GTA IV, they make all of the car tires in the game and some of the headlights.
Atomic serves the same purpose as it did in GTA IV but now they have their very own sponsorship blimp in the sky advertising their products.